Air-fuel control in prevaporizer type combustion chambers



March 29, 1960 R. M. SCHIRMER ETA!- 3191 AIR-FUEL CONTROL IN PREVAPORIZER TYPE COMBUSTION CHAMBERS Filed Jan. 29, 1953 2 sheets sheet I,

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ATTORNEYS March 29, 196% sc ETAL 2,930,191

AIR-FUEL CONTROL IN PREVAPORIZER TYPE COMBUSTION CHAMBERS Filed Jan. 29, 1953 2 Sheets-Sheet 2 29 PRIMARY AIR INLET 1. y L n firm-J INVENTORS EIZIE'omm/ w 1-\\\\\ BY EMJcluimer A TTOPNEKS AIR-FUEL CONTROL IN PREVAPORIZERTYPE V COMBUSTION CHAMBERS Robert M. Schirmer and Ellsworth H. Fromm, Bartlesville-,-kln., assignors to Phillips Petroieum 'Qompany, a corporation of Delaware Application January 29,1953, Serial No. 333,870 6 Claims. (or. eoaaza ance with the fuel flow or pressure in the fuel lines to the vaporizer tubes to regulate the amountof air supplied to the combustion zone and to insure vaporization of the liquid fuel.

In one type of aircraft propulsion system, comprising an air compressor, fuel burner means atv the compressor outlet, and a gas turbine driven by the combustion products and air heated thereby and mechanically driving the compressor, thrust is developed by reaction arising out of the expansion of the stream of .gas through a nozzle or jet. One established practice in the art is the introduction of the fuel into the combustion chamber in the form of a vapor through vaporizer tubes mounted in the upstream end of the tube plate and extending into the flame or burner tube. The tube plate forms a partial closure at the upstream end of the flame tube so that air from the compressor is directed into the vaporizer tubes, around the flame tube and through holes in the flame tube into the combustion zones, and through primary air ducts located in the tube plate and directing air into the combustion zones. The combustion chamber ordinarily comprises a burner tube surrounded by a shell so that the air furnished by the air compressor is divided into primary and secondary air. The primary air enters the burner tube head and in some cases is admittedto the front portion of the burner tube through holes in the burner tube wall. The air entering the prevaporizer tube is a portion of the primary air. The remaining air flows through the annular space between the burner tube wall and the shell of the combustion chamber and is admitted to the burner tube downstream from the flame front and is designated as secondary air.

Air and liquidv fuel are introduced into the upstream ends of the vaporizer tubes and the fuel is vaporized in the tubes which are exposed to the combustion flames. The downstream ends of the vaporizer tubes change direction through 180 and the vaporized fuel and air mixture formed in the tubes is discharged upstream into the air entering through the primary air inlet. The air flowing through the vaporizer tubes assists in vaporization of the fuel by reducing the temperature required for complete vaporization of the fuel. The air also serves to reduce the deposition of carbon, resulting from overheating of the fuel, on the wallsof the tubes and aids in the transport of liquid and unvaporized fuel through the vaporizer tubes. The air entering through the primary air inlet. aids in. the completion of combustion of the vaporized fuel discharged from the vaporizer tubes.

Patented Mar. 29, 1960 In engines employing tubular type combustionchambers, a number of vaporizer tubes may be provided in each combustion chamber and arranged symmetrically around a single primary 'air duct, or inlet. Usually a separate primary air duct is provided for each vaporizer tube. In engines employing an annular type combustion chamber, the same arrangement of vaporizer tubes and primary air ducts may also be employed. Each vaporizer tube is'an independent source of fuel supply and a uniform discharge of vaporized fuel, in accordance with the combustion requirements of the particular operating conditions of the engine, must be maintained in order to provide highly efiicient and stable combustion in the combustion chamber.

The present invention discloses a method and apparatus for regulating the amount of air supplied to the vaporizer tube and to the primary air inlet in the burner tube head in response to a change in the pressure in the fuel line so as to-regulate the air-fuel ratio in the primary combustion zone and to maintain vaporization of the liquid fuel in the prevaporizer tubes to thereby improve combustion stability of the burner configuration. Thus according to the practice of our invention the opening in an adjustable air orifice located in the inlet end of a J-type vaporizer tube and/ or located at the discharge end of a primary air duct is increased with an increase in the pressure in the fuel line to the vaporizer tube so as to admit more air into the vaporizer tube and/or the primary air duct and to maintain the air-fuel ratio of the mixture in the primary combustion zone in a range where efiicient and stable combustion takes place. This method of control assists in the maintenance of a stoichiometric mixture of air and fuel in the primary combustion zone above a critical lean value so that stable combustion is maintained over a wide range of operating conditions. The amount of primary air and prevaporizer tube air is increased with an increase in the amount of fuel supplied the combustion zone and similarly the amount of air is reduced when the pressure in the fuel line is reduced as a result of decreasing the amount of fuel supplied to the combustion chamber.

The following objects are'attained by the aspects ofthis invention. I

it is an object of this invention to provide a method for controllingthe air-fuel ratio in the combustion chamher in a prevaporizer type continuous combustionpower plant.

It is another object to provide a method for regulating the air-fuel ratio in a combustion zone in response to the amount of fuel supplied the combustion zone.

it is another object to provide a method for maintaining vaporization of the fuel in a prevaporizer tube of a continuous combustion chamber With varying fuel flow.

It is another object to provide an apparatus for controlling the air-fuel ratio in a continuous combustion chamber in response to the amount of fuel supplied the combustion chamber.

at least one of It is another object to provide an apparatus for con- V trolling the amount of air admittedto the prevaporizer tube in a combustion chamber in response to the amount of fuel supplied the combustion chamber.

It is another object to provide an apparatus for controlling the amount of primary air admitted to a continuous combustion chamber in response to the amount of fuel supplied the combustion chamber.

Other objects will be apparent to one skilled in the art upon reading the following description in which reference is made to the attached drawing wherein;

Figure l is a longitudinal sectional view through a dame tube of a jet engine showing one form of the in vention;

Figure 2 shows another embodiment of the invention;

Figure 3 shows another embodiment of the invention; and

Figure 4 shows a modification of one embodiment of the invention.

In Figure 1 a flame tube of a jet engine combustion chamber is indicated at 10. The simplified embodiment shown contains a J-type vaporizer tube 11 mounted in a flame tube head 12 adjacent a primary air duct 13. This invention is also applicable in a design in which a plurality of vaporizer tubes and primary air ducts are utilized. The flame tube is shown containing only secondary air holes 14 but some primary air holes located near the flame tube head 12 can also be used if desired. The flame tube shown can be considered to be from either a tubular type combustion chamber or an annular type combustion chamber. Ignition means, such as a sparkplug, are well known in the art and are not shown in this simplified drawing. A fuel line 16 is disposed within air duct 18 and contains therein as an integral part thereof a linearly expandable section shown in the drawing as bellows 15. At a point upstream from bellows 15, the fuel line is attached rigidly to the flame tube head 12 by a supporting member 17. The upstream end of vaporizer tube 11, which is of a diameter somewhat different than that of air duct 18, is rigidly attached to flame tube head 12 concentric with air duct 18. The transition section 19 be tween air duct 18 and vaporizer tube 11 is frustro-conical in cross section. Rigidly attached to the end of fuel line 16 and extending into vaporizer tube 11 is a valve head 20 containing an orifice 21 therethrough for admittance of fuel. Valve head 20 which, in combination with transition section 19, forms an orifice through which air can pass into the vaporizer tube 11. The orifice in valve head 20 through which fuel flows from fuel line 16 into the vaporizer tube 11 maintains a back pressure upon the fuel line during normal operation of the engine. The valve head 20 is located with respect to transition section 19 and in relation of the state of expansion of bellows that the orifice 21 permits suflicient flow of air into vaporizer tube 11 to establish stable combustion under idle-feed operating conditions. Upon increasing the fuel flow, bellows 15 expands, enlarging the crosssectional area of valve opening 21, so as to admit more air into vaporizer tube 11. In a similar manner, a. decrease in fuel flow results in a reduction in size of valve opening 21 and air flow through vaporizer tube 11.

In the modification in Figure 2, the primary air to the combustion chamber is regulated rather than the air used in vaporizing the fuel. In Figure 2, fuel line 16 situated in air duct 18 is attached to flame tube head 12 by rigid support 17 and contains an orifice in the downstream end of fuel line 16. Branch fuel line 27 extends into primary air inlet 13 and contains a linearly expandable section as an integral part thereof shown as bellows 22. Fuel line 27 is secured from movement upstream from bellows 22 by rigid low air resistance supports 23. Valve stem 24 and valve head 25 are secured to bellows 22 so as to form a valve between valve head 25 and an extension 26 of primary air inlet 13 which forms a seat from valve head 25. Thus an increase in fuel pressure in fuel line 16 and branch line 27 results in opening the valve from the valve head 25 and valve seat 26 so as to admit more primary air to the combustion chamber.

Figure 3 shows a modification of this invention wherein the air used in the vaporizer tube and the air passing through the primary air duct is regulated by a valve in the vaporizer tube and in the primary air inlet both being operated in response to the pressure in the fuel line.

In Figure 4 is shown a modification of this invention wherein the branch fuel line 27, as shown in Figure 2, has incorporated therein a slidable section 31 so that an increase in pressure in the fuel line forces valve head 25 against the tension of a coil spring 32 so as to open the valve between valve head 25 and valve seat 26.

This invention provides a positive, automatic control of the air-fuel ratio in a continuous combustion power plant which is simple, dependable, compact and light in weight. These characteristics are essential in aircraft engine control and all of them are embodied in this invention.

Variations and modifications are possible within the scope of the disclosure of this invention, the essence of which is a method and apparatus for admitting a greater amount of air to the vaporizer and the primary combustion chamber by elongation of the fuel line in response to an increase in fuel flow.

We claim:

1. A continuous combustion chamber comprising, in combination, a burner tube having inlets and an outlet; a vaporizer disposed within said tube connected to and communicating with an inlet; a linearly expandable fuel line disposed within said inlet and terminating in an orifice in said vaporizer; a valve operatively connected to said fuel line so as to admit more air to said vaporizer in response to an increase in pressure in said fuel line; and a valve in a remaining inlet operatively connected to said fuel line so as to admit more air to said burner tube in response to an increase in pressure in said fuel line.

2. A continuous combustion chamber comprising, in combination, a burner tube having inlets and an outlet; a vaporizer tube disposed within said burner tube connected to and communicating with an inlet, said vaporizer tube being greater in cross-section than said inlet thereby forming a valve seat; and a pressure responsive, linearly expandable fuel line disposed within said inlet and terminating within said vaporizer tube in an end member having a cross-section greater than that of said inlet so as to form a valve opened by fuel line pressure, said end member having an orifice therethrough for passage of fuel to said vaporizer.

3. A continuous combustion chamber comprising in combination a burner tube having inlets and an outlet; 21 vaporizer, having a greater cross-section than that of a first inlet disposed within said burner tube, operatively connected to and communicating with said inlet so as to form a valve seat; a linearly expandable fuel line disposed within said inlet terminating within said vaporizer in an end member having a cross-section greater than that of said inlet so as to form a valve opened by fuel line pressure, said end member having an orifice therethrough for passage of fuel to said vaporizer; and a branch line extending from said fuel line having a linearly expandable section thereof disposed within a second inlet and terminating in a closed end of greater cross-section than that of said inlet and within said burner tube so as to form a valve admitting more air in response to fuel line pressure.

4. The combustion chamber of claim 1 wherein the linearly expandable fuel line comprises a fuel line having incorporated therein as an integral part thereof a bellows.

5. The combustion chamber of claim 3 wherein the linearly expandable fuel line sections comprise bellows.

6. The combustion chamber of claim 2 wherein the linearly expandable fuel line section comprises a bellows.

References Cited in the file of this patent UNITED STATES PATENTS 2,005,832 Vidalie June 25, 1935 2,111,484 Woodson Mar. 15, 1938 2,418,712 Heymann Apr. 8, 1947 2,445,466 Arnhyrn July 20, 1948 2,637,975 Hague May 12, 1953 2,655,787 Brown Oct. 20, 1953 2,661,794 Shorrock Dec. 8, 1953 FOREIGN PATENTS 339,314 Great Britain Dec. 5, 1950 407,920 Great Britain June 28, 1932 619,353 Great Britain Mar. 8, 1949 670,187 Great Britain Apr. 16, 1952 

